The present invention relates to a traction distributing apparatus for a motor vehicle, which allows active control of the ratio of traction to be distributed to right and left wheels.
One of the traction distributing apparatus for a motor vehicle is disclosed, for example, in JP-A 3-50028. This apparatus includes, in a housing, a differential gear for transmitting traction to right-wheel and left-wheel shafts in such a way as to eliminate the difference in the number of revolutions between right and left wheels, and a hydraulic motor for providing relative torque to the two shafts as required. Upon cornering of the vehicle, for example, the hydraulic motor is actuated to allow an outside wheel to receive greater torque than an inside wheel, producing a yaw moment in the vehicle.
The hydraulic motor includes a casing mounted to an inner peripheral wall of a differential casing, an inner rotor mounted to one of the wheel shafts, and inner passages connected to supply/discharge passages of the housing through annular passages formed in the outer peripheral surface of the casing. Each annular passage is defined by a pair of resin seal rings fixed to the inner peripheral surface of the housing or the outer peripheral surface of the motor casing. By making a peripheral end of each seal ring slidably closely contact the inner peripheral surface of the housing or the outer peripheral surface of the motor casing, the hydraulic motor can always ensure supply/discharge of hydraulic fluid regardless of rotation of the motor casing.
In the above traction distributing apparatus, the resin seal rings are disposed between the inner peripheral surface of the housing and the outer peripheral surface of the motor casing, and the annular passages defined by the seal rings ensure fluid communication between the supply/discharge passages of the housing and the inner passages of the hydraulic motor. With such structure, the seal rings are difficult to surely be mounted without any possible leakage of hydraulic fluid, and are easy to deteriorate with time due to their slide contact with the peripheral surface of the housing or the motor casing, having an inconvenience of difficult maintenance of the stable sealing performance during a long period of time. Moreover, in the case of a hydraulic motor having inner passages formed in an inner rotor, further connection should be carried out between the passages of the inner rotor and passages of a motor casing in the same way, resulting in more difficult mounting of the seal rings and easier occurrence of leakage of hydraulic fluid with years of use.
It is, therefore, an object of the present invention to provide a traction distributing apparatus for a motor vehicle, which is easy to assemble, and allows fluid communication between the supply/discharge passages of the housing and the inner passages of the inner rotor of the hydraulic motor to continuously surely be maintained without any leakage of hydraulic fluid.